In recent years, some industries have actively been using supercritical fluid chromatography (SFC), supercritical fluid extraction (SFE), or any other supercritical fluid system. The reason for this is that the solubility of a supercritical fluid can be changed by changing it's pressure and temperature. Among the materials used as the supercritical fluid, carbon dioxide (CO2) is frequently used as the supercritical fluid in analysis and preparative usage, because CO2 is advantageous not only in that it can be transferred to a supercritical fluid under relatively mild conditions, that is, at a critical temperature of 31.1° C. and a critical pressure of 7.38 MPa, but also in that CO2 is chemically inert and highly pure CO2 is available at low cost. To increase the degree of freedom of the separation mode in the analysis or preparative application, CO2 mixed with organic solvents is also widely used. The organic solvents are also called a modifier. The modifier is added to liquid-phase CO2 at a rate of approximately 50% at the maximum.
Japanese Patent Laid-Open No. 2002-71534 discloses a sample collection method used in any of the supercritical fluid systems described above which involves discharging a supercritical fluid containing a sample separated and eluted in a column (a mixed fluid of liquid-phase CO2 and organic solvents) through an automatic back pressure regulator, transferring the supercritical fluid through a multi-port distribution value to a large number of corresponding transfer tubes, and loaded the supercritical fluid from the transfer tubes into bottles in a collection chamber maintained at a predetermined pressure (20 to 100 psi≈0.14 to 0.69 MPa). In this process, to prevent the CO2 from abruptly evaporating and the organic solvents from becoming an aerosol and scattering, the transfer tubes are heated and the collection chamber and the bottles are maintained under the pressure described above. There is a possibility that flow path is cooled by endoergic reaction owing to adiabatic expansion of CO2, and thus the sample tends to be a solid. In order to inhibit plugging the tubes and the chamber with the solid, they are heated. The Gas-liquid-phase fluid is spirally delivered into the bottles. The gas-phase CO2 is discharged from the bottles under a predetermined pressure, and the liquid-phase organic solvents are collected in the bottles.
Japanese Patent Laid-Open No. 2007-120972 discloses a sample collection apparatus in a supercritical fluid system for collecting a multi-constituent sample injected into a mixed fluid of liquid-phase CO2 and a modifier. The apparatus involves separating the sample in a column for each of the constituents, reducing the pressure of the supercritical fluid containing each of the eluted samples in an automatic back pressure regulator to a pressure close to the atmospheric pressure, fractionating the gas containing the thereby formed aerosol through a flow path distribution valve, delivering each of the fractionated gases through the corresponding line to the corresponding Gas-liquid separator to separate the gas-phase CO2 and spirally spray the liquid component containing the sample in the Gas-liquid separator to form droplets, and causing the droplets to fall into a collection bottle connected to the Gas-liquid separator. That is, the gas-phase CO2 and the liquid component are separated from each other in the slightly pressurized Gas-liquid separator.
In addition to the Gas-liquid separator disclosed in Japanese Patent Laid-Open No. 2007-120972, there is a cap-type Gas-liquid separator 410, which is attached, when used, to an upper-end opening of a collection container 400, as shown in FIGS. 19A to 19C. That is, FIG. 19A is a plan view of the collection container 400 to which the cap-type Gas-liquid separator 410 is attached. FIG. 19B is a longitudinal cross-sectional view of the assembled structure. FIG. 19C is a side view of the assembled structure viewed in the direction indicated by the line [C]-[C] in FIG. 19B. As shown in FIG. 19B, the Gas-liquid separator 410 includes a Gas-liquid separating unit 421 most of which is inserted into the collection container 400, an exhausting gas unit 441 provided on the Gas-liquid separating unit 421, and a clipping unit 451 used to attach the Gas-liquid separator 410 to the collection container 400.
The Gas-liquid separating unit 421 is as a whole placed on the upper end of the collection container 400 and fixed thereto by a seat 422. An introduction line 423 for introducing a gas containing a fractionated aerosol is provided on a side of an upper end portion of the Gas-liquid separating unit 421 so that the gas flows into a cylindrical space S1, which will be described later, in a tangential direction. A heater 424 having the cylindrical space S1 is provided downstream of the introduction line 423. A sintered stainless filter 432 having a cylindrical shape with a bottom is fixed to the lower end of the heater 424 by a fixing buffer plate 431 and hanged therefrom. The structure described above forms a separating unit 433. A space S2 surrounded by the sintered filter 432 connects with the space S1 in the heater 424.
In the exhausting gas unit 441, a discharge duct 443 is connected to the upper end of the space S1 in the heater 424, and a discharge duct 444 is connected to the discharge duct 443. An upper clipping part 453 of the clipping unit 451 is attached to an upper end portion of the Gas-liquid separating unit 421, and the Gas-liquid separator 410 is attached and detached to and from the collection container 400 via an openable lower clipping part 454 that grips the neck of the collection container 400. The lower clipping part 454 is opened and closed by operating a movable lever 452 of the clipping unit 451.
The gas containing a liquid component aerosol introduced through the introduction line 423, after moved from the space S1 in the heater 424 to the space S2 in the separating unit 433, is discharged through the sintered stainless filter 432 into the collection container 400 in all directions, whereby the linear velocity of the fluid is significantly reduced. As a result, the adhesion between the liquid component and the sintered stainless filter 432 is greater than the force that causes the liquid component passing through the micro pore in the sintered stainless filter 432 to scatter, whereby the scattering of the liquid component will be suppressed. The liquid component moves downward due to the gravity and drops through the bottom of the sintered stainless filter 432 into the collection container 400.